I asked polished bliss about Titanium (and to be fair to them it was higher cost so they would've made more from it) and they said that although it is tougher they felt that the finish of Carbon was better suited to metallic black cars IIRC.
Current: E90 335d (May 2007) | Black/Black | Prof Hifi | Prof Nav | 6FL | Fully Electric Seats | Xenons | Folding Mirrors | PDC
Previous: 325ci Conv. Black/Black with lots of ACS
Previous: z3 3.0 Silver with Black&Red Leather